Thermoacoustic Imaging with Magnetic Nanoparticles under Envelope Short Pulse Alternating Magnetic Field Based on Magnetic Susceptibility Distribution Variation

The magnetically mediated thermoacoustic imaging with magnetic nanoparticles (MNPs), which is excited by nonuniform pulsed envelope magnetic field, is constructed here, and the results of the magnetic susceptibility distribution of nanoparticles are extracted. In this paper, the theoretical model of the nonuniform magnetic field based on space-time separation is solved, and the Rosensweig model is used to obtain the heat generation of MNPs under the excitation of the pulsed envelope magnetic field. To solve the inverse problem, the heat source distribution is calculated by the time inversion method according to the sound pressure propagation formula under adiabatic conditions. After filtering out the effect of the nonuniform magnetic field, the magnetic susceptibility distribution can be obtained. The reconstruction results from simulation and experiment are consistent with the original distribution of MNPs and the distribution of the magnetic susceptibility. This method is expected to be applied to the precise diagnosis and treatment of tumors and provide a new idea for the precise localization and distribution image reconstruction of nanoparticles in vivo.